Advanced Materials

Cover image for Vol. 24 Issue 6

February 7, 2012

Volume 24, Issue 6

Pages 709–849

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. Micromachines: Magnetic Helical Micromachines: Fabrication, Controlled Swimming, and Cargo Transport (Adv. Mater. 6/2012) (page 709)

      Soichiro Tottori, Li Zhang, Famin Qiu, Krzysztof K. Krawczyk, Alfredo Franco-Obregón and Bradley J. Nelson

      Article first published online: 31 JAN 2012 | DOI: 10.1002/adma.201290025

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      A simple and general fabrication method for magnetic helical micromachines with or without claw-like protrusions is reported by Li Zhang and co-workers on page 811. The dynamics of motion control reveal that corkscrew motion can always be generated when the input frequency of the rotating magnetic field is sufficiently high. The micromachines exhibit excellent swimming behavior, low cytotoxicity, and are capable of 3D cargo transport in fluid.

  2. Inside Front Cover

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. Porous Materials: Energy-Efficient Dehumidification over Hierachically Porous Metal–Organic Frameworks as Advanced Water Adsorbents (Adv. Mater. 6/2012) (page 710)

      You-Kyong Seo, Ji Woong Yoon, Ji Sun Lee, Young Kyu Hwang, Chul-Ho Jun, Jong-San Chang, Stefan Wuttke, Philippe Bazin, Alexandre Vimont, Marco Daturi, Sandrine Bourrelly, Philip L. Llewellyn, Patricia Horcajada, Christian Serre and Gérard Férey

      Article first published online: 31 JAN 2012 | DOI: 10.1002/adma.201290026

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      The energy-efficient dehumidification over hier-archically porous metal-organic frameworks (MOFs) with hydrothermal stability is reported on page 806 by Jong-San Chang and co-workers. Their promising water sorption properties lead to a new type of advanced water adsorbents for the effective utilization of low-grade thermal energy as well as solar energy. These MOFs would be potential alternatives to commercial water adsorbents, which are used for industrial or indoor desiccant applications such as desiccant dehumidifiers/humidifiers, gas dryers, adsorptive air-conditioning systems, fresh water production, and adsorption heat transformation.

  3. Masthead

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. Masthead: (Adv. Mater. 6/2012)

      Article first published online: 31 JAN 2012 | DOI: 10.1002/adma.201290027

  4. Contents

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. Contents: (Adv. Mater. 6/2012) (pages 711–718)

      Article first published online: 31 JAN 2012 | DOI: 10.1002/adma.201290022

  5. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. Investigating the Role of Grain Boundaries in CZTS and CZTSSe Thin Film Solar Cells with Scanning Probe Microscopy (pages 720–723)

      Joel B. Li, Vardaan Chawla and Bruce M. Clemens

      Article first published online: 9 JAN 2012 | DOI: 10.1002/adma.201103470

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      Scanning Kelvin probe microscopy (SKPM) measurements reveal a higher positive surface potential at the grain boundaries (GBs) as compared to the grain while conductive atomic force microscopy (C-AFM) measurements show higher current flow in the vicinity of the GBs of Cu2ZnSnS4 (CZTS) and Cu2ZnSn(S,Se)4 (CZTSSe). These results demonstrate the enhanced minority carrier collection taking place at the GBs of CZTS and CZTSSe.

    2. Organic Exciton Multiferroics (pages 724–727)

      Shenqiang Ren and Manfred Wuttig

      Article first published online: 28 DEC 2011 | DOI: 10.1002/adma.201104250

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      For the first time the observation of substantial visible light-, electrically and mechanically induced changes of the magnetization of an organic exciton multiferroic consisting of single crystal P3HT doped with C60 is reported. The observations open new avenues for exciton based spintronic devices.

    3. Design of Transparent Anodes for Resonant Cavity Enhanced Light Harvesting in Organic Solar Cells (pages 728–732)

      Nicholas P. Sergeant, Afshin Hadipour, Bjoern Niesen, David Cheyns, Paul Heremans, Peter Peumans and Barry P. Rand

      Article first published online: 3 JAN 2012 | DOI: 10.1002/adma.201104273

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      The use of an ITO-free MoO3/Ag/MoO3 anode to control the photon harvesting in PCDTBT:PC70BM solar cells is proposed. At first sight, the fact that these anodes possess reduced far-field transmission compared to ITO may seem to be a disadvantage. But, despite this, we show that by carefully tuning the resonant optical cavity we can enhance the external quantum efficiency close to the band edge of PCDTBT, resulting in high photocurrent and power conversion efficiency on par with ITO.

    4. Kinetically Assembled Nanoparticles of Bioactive Macromolecules Exhibit Enhanced Stability and Cell-Targeted Biological Efficacy (pages 733–739)

      Adam W. York, Kyle R. Zablocki, Daniel R. Lewis, Li Gu, Kathryn E. Uhrich, Robert K. Prud'homme and Prabhas V. Moghe

      Article first published online: 2 JAN 2012 | DOI: 10.1002/adma.201103348

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      Kinetically assembled nanoparticles are fabricated from an advanced class of bioactive macromolecules that have potential utility in counteracting atherosclerotic plaque development via receptor-level blockage of inflammatory cells. In contrast to micellar analogs that exhibit poor potency and structural integrity under physiologic conditions, these kinetic nanoparticle assemblies maintain structural stability and demonstrate superior bioactivity in mediating oxidized low-density lipoprotein (oxLDL) uptake in inflammatory cells.

    5. Unusually Large Enhancement of Thermopower in an Electric Field Induced Two-Dimensional Electron Gas (pages 740–744)

      Hiromichi Ohta, Taku Mizuno, Shijian Zheng, Takeharu Kato, Yuichi Ikuhara, Katsumi Abe, Hideya Kumomi, Kenji Nomura and Hideo Hosono

      Article first published online: 3 JAN 2012 | DOI: 10.1002/adma.201103809

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      Unusually large thermopower modulation is demonstrated using a field effect transistor structure on a thermoelectric material. An electric field application provides an extremely thin (∼2 nm) two-dimensional electron gas (2DEG), which exhibits unusually large thermopower, approximately five times larger than that of the bulk. The present electric field induced 2DEG approach may accelerate the development of nanostructures for high performance thermoelectric materials.

    6. Double-Shelled CoMn2O4 Hollow Microcubes as High-Capacity Anodes for Lithium-Ion Batteries (pages 745–748)

      Liang Zhou, Dongyuan Zhao and Xiong Wen Lou

      Article first published online: 29 DEC 2011 | DOI: 10.1002/adma.201104407

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      Novel double-shelled CoMn2O4 hollow microcubes with nanometer-sized building blocks have been prepared by a facile co-precipitation and annealing method. In virtue of the unique structural features, the resultant CoMn2O4 hollow structures exhibit high specific capacity (∼830 mA h g−1 at 200 mA g−1) and good cycling performance as an anode material for lithium-ion batteries.

    7. Innovative Collagen Nano-Hydroxyapatite Scaffolds Offer a Highly Efficient Non-Viral Gene Delivery Platform for Stem Cell-Mediated Bone Formation (pages 749–754)

      Caroline M. Curtin, Gráinne M. Cunniffe, Frank G. Lyons, Kazuhisa Bessho, Glenn R. Dickson, Garry P. Duffy and Fergal J. O'Brien

      Article first published online: 2 JAN 2012 | DOI: 10.1002/adma.201103828

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      The ability of nano-hydroxyapatite (nHA) particles developed in-house to act as non-viral delivery vectors is assessed. These nHA particles are combined with collagen to yield bioactive, biodegradable collagen nano-hydroxyapatite (coll-nHA) scaffolds. Their ability to act as gene-activated matrices for BMP2 delivery is demonstrated with successful transfection of mesenchymal stem cells (MSCs) resulting in high calcium production.

    8. Targeting Gold Nanoshells on Silica Nanorattles: a Drug Cocktail to Fight Breast Tumors via a Single Irradiation with Near-Infrared Laser Light (pages 755–761)

      Huiyu Liu, Tianlong Liu, Xiaoli Wu, Linlin Li, Longfei Tan, Dong Chen and Fangqiong Tang

      Article first published online: 28 DEC 2011 | DOI: 10.1002/adma.201103343

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      The drug-loaded, transferrin and poly(ethylene glycol) (PEG)-functionalized gold nanoshells on silica nanorattles (pGSNs-Doc-Tf) can combine the active targeting, passive targeting, remote-controlled photothermal therapy together with chemotherapy to completely kill tumor cells via a single irradiation with near-infrared laser light.

    9. The Memristive Magnetic Tunnel Junction as a Nanoscopic Synapse-Neuron System (pages 762–766)

      Patryk Krzysteczko, Jana Münchenberger, Markus Schäfers, Günter Reiss and Andy Thomas

      Article first published online: 5 JAN 2012 | DOI: 10.1002/adma.201103723

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      A comprehensive study on the analogy of memristive magnetic tunnel junctions and biological neural systems is performed. It is demonstrated that the continuous, bipolar resistance change due to resistive switching can be used to mimic the synaptic connection between neurons. Particularly, the timing-dependent plasticity is observed. Further, the magnetization switching driven by spin-transfer torque in combination with back-hopping is used to generate current spikes. These spikes show remarkable similarities with the signals generated by excited neurons.

    10. Particle Stabilization of Oil-in-Water-in-Air Materials: Powdered Emulsions (pages 767–771)

      Ryo Murakami, Hiroshi Moriyama, Masahiro Yamamoto, Bernard P. Binks and Anaïs Rocher

      Article first published online: 2 JAN 2012 | DOI: 10.1002/adma.201104089

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      Drops of a particle-stabilised oil-in-water emulsion are encapsulated in air by using hydrophobic silica particles. Such systems, termed oil-in-water-in-air powdered emulsions, show free-flowing behavior. Successful preparation of the material is achieved by preventing oil droplets from creaming and coalescing.

    11. Elastic Properties of Freely Suspended MoS2 Nanosheets (pages 772–775)

      Andres Castellanos-Gomez, Menno Poot, Gary A. Steele, Herre S. J. van der Zant, Nicolás Agraït and Gabino Rubio-Bollinger

      Article first published online: 9 JAN 2012 | DOI: 10.1002/adma.201103965

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      The elastic deformation of few layers (5 to 25) of thick, freely suspended MoS2 nanosheets by means of a nanoscopic version of a bending test experiment, carried out with the tip of an atomic force microscope is reported. Young's modulus of these nanosheets is extremely high (E = 0.33 TPa), comparable to that of graphene oxide, and the deformations are reversible up to tens of nanometers.

    12. Super-Compressibility of Ultralow-Density Nanoporous Silica (pages 776–780)

      S. O. Kucheyev, M. Stadermann, S. J. Shin, J. H. Satcher Jr., S. A. Gammon, S. A. Letts, T. van Buuren and A. V. Hamza

      Article first published online: 9 JAN 2012 | DOI: 10.1002/adma.201103561

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      Porosity generally embrittles ceramics. In contrast to such expectations, this report demonstrates that an effective fracture strain of nanoporous silica aerogels increases with increasing porosity. At ultralow relative densities of <0.5%, nanoporous monoliths start exhibiting super-compressible deformation with effective fracture strains of >50%. This is attributed to consequences of an increase in the aspect ratio of ligaments with decreasing density.

    13. Conduction Through Viscoelastic Phase in a Redox-Active Ionic Liquid at Reduced Temperatures (pages 781–784)

      Verner K. Thorsmølle, Daniel Topgaard, Jan C. Brauer, Shaik M. Zakeeruddin, Björn Lindman, Michael Grätzel and Jacques-E. Moser

      Article first published online: 3 JAN 2012 | DOI: 10.1002/adma.201104230

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      The phase diagram of the redox active ionic liquid 1-methyl-3-propylimidazolium iodide (PMII) is examined as a function of temperature and iodine concentration. Beyond a threshold concentration of 3.9 M, the formation of higher polyiodides gives rise to a viscoelastic phase upon cooling. Despite of the very high viscosity of such polyiodide-containing PMII melts a strikingly high conductivity is maintained through Grotthuss-type bond exchange and ionic conduction.

    14. Perfluorohexane-Encapsulated Mesoporous Silica Nanocapsules as Enhancement Agents for Highly Efficient High Intensity Focused Ultrasound (HIFU) (pages 785–791)

      Xia Wang, Hangrong Chen, Yu Chen, Ming Ma, Kun Zhang, Faqi Li, Yuanyi Zheng, Deping Zeng, Qi Wang and Jianlin Shi

      Article first published online: 5 JAN 2012 | DOI: 10.1002/adma.201104033

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      An inorganic enhancement agent (EA) for high-intensity focused ultrasound (HIFU) imaging based on mesoporous silica nanocapsules is presented. The pronounced coagulative necrosis effects demonstrate, both in vitro and in vivo, that the EA can be developed as a highly promising theranostic agent for effective HIFU imaging and therapy owing to its high stability, efficient perfluorohexane loading and release, enhanced tumor ablation capability, and easy uptake by target tissues.

    15. Fabrication of an Efficient Light-Scattering Functionalized Photoanode Using Periodically Aligned ZnO Hemisphere Crystals for Dye-Sensitized Solar Cells (pages 792–798)

      Ki Seok Kim, Hui Song, Sang Hoon Nam, Sang-Mook Kim, Huisu Jeong, Won Bae Kim and Gun Young Jung

      Article first published online: 3 JAN 2012 | DOI: 10.1002/adma.201103985

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      A periodically aligned submicron ZnO hemispheres array was embedded into a TiO2 nanoparticulate thin film (thickness; ca. 12 μm) as a photoanode for dye-sensitized solar cells (DSSCs). The ZnO hemisphere array provided light scattering centers that excited more dyes and direct electron pathways to the electrodes, which is beneficial for high efficiency DSSCs.

  6. Frontispiece

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. Graphene: Integrating Water-Soluble Graphene into Porphyrin Nanohybrids (Adv. Mater. 6/2012) (page 799)

      J. Malig, C. Romero-Nieto, N. Jux and D. M. Guldi

      Article first published online: 31 JAN 2012 | DOI: 10.1002/adma.201290023

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      Dirk Guldi and co-workers demonstrate on page 800 the realization of high-quality graphene flakes by means of solution processing with tightly interacting constituents to which a porphyrin has been self-assembled. These were integrated into novel photo-electrodes by means of layer-by-layer deposition that give rise to appreciable photocurrents.

  7. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. Integrating Water-Soluble Graphene into Porphyrin Nanohybrids (pages 800–805)

      J. Malig, C. Romero-Nieto, N. Jux and D. M. Guldi

      Article first published online: 29 DEC 2011 | DOI: 10.1002/adma.201103697

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      Exfoliation of graphite by a positively charged pyrene derivative was achieved in water and electronic communication by non-invasive electrostatic interaction with a negatively charged porphyrin was accomplished and proven photospectroscopically. The oppositely charged components were assembled through layer by layer deposition.

    2. Energy-Efficient Dehumidification over Hierachically Porous Metal–Organic Frameworks as Advanced Water Adsorbents (pages 806–810)

      You-Kyong Seo, Ji Woong Yoon, Ji Sun Lee, Young Kyu Hwang, Chul-Ho Jun, Jong-San Chang, Stefan Wuttke, Philippe Bazin, Alexandre Vimont, Marco Daturi, Sandrine Bourrelly, Philip L. Llewellyn, Patricia Horcajada, Christian Serre and Gérard Férey

      Article first published online: 12 DEC 2011 | DOI: 10.1002/adma.201104084

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      Hierarchically porous metal–organic frameworks with mesoporous cages are demonstrated to behave as promising water adsorbents in energy-efficient dehumidification. Their low temperature desorption properties for water with huge sorption uptakes are essential for various water sorption applications including desiccant dehumidification and fresh water production.

    3. Magnetic Helical Micromachines: Fabrication, Controlled Swimming, and Cargo Transport (pages 811–816)

      Soichiro Tottori, Li Zhang, Famin Qiu, Krzysztof K. Krawczyk, Alfredo Franco-Obregón and Bradley J. Nelson

      Article first published online: 2 JAN 2012 | DOI: 10.1002/adma.201103818

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      A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated. The magnetic helical devices exhibit varying magnetic shape anisotropy, yet always generate corkscrew motion using a rotating magnetic field. They also exhibit good swimming performance and are capable of pick-and-place micromanipulation in 3D. Cytotoxicity of the devices was investigated using mouse myoblasts.

    4. Directional Transport of Polymer Sheet and a Microsphere by a Rationally Aligned Nanowire Array (pages 817–821)

      Weiwei Wu, Li Cheng, Suo Bai, Zhong Lin Wang and Yong Qin

      Article first published online: 2 JAN 2012 | DOI: 10.1002/adma.201104085

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      Aligned oblique nanowire arrays (AONWAs; top image) with controllable obliquity, NW diameter, length, and density are produced by a novel method. A mechanism of array formation is proposed and it is demonstrated that the surface structure of AONWAs can be utilized to transport objects ranging from a polystyrene microsphere to a macroscopic PET sheet (lower figures). Unidirectional wetting of the surface and the relation between the anisotropy of the wetting and the NWs' obliquity are described. Potential applications of the AONWAs include fluidic diodes, drug delivery systems, and self-cleaning without a liquid.

    5. Diffusion – the Hidden Menace in Organic Optoelectronic Devices (pages 822–826)

      Arthur R. G. Smith, Kwan H. Lee, Andrew Nelson, Michael James, Paul L. Burn and Ian R. Gentle

      Article first published online: 29 DEC 2011 | DOI: 10.1002/adma.201104029

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      In a film stack of bathocuproine (BCP) (electron transport layer), fac -tris(2-phenylpyridyl)iridium(III) [Ir(ppy)3] blended in 4,4′-bis(N -carbazolyl)biphenyl (CBP) (light-emitting layer), and 4,4′,4″-tris(N -carbazolyl)triphenylamine (TCTA) (hole transport layer), the BCP and Ir(ppy)3:CBP layers rapidly interdiffuse by anomalous Fickian diffusion. Diffusion leads to a decrease of up to 33% in the solid-state emission but no change in color.

  8. Frontispiece

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. All-Organic Photopatterned One Diode-One Resistor Cell Array for Advanced Organic Nonvolatile Memory Applications (Adv. Mater. 6/2012) (page 827)

      Tae-Wook Kim, David F. Zeigler, Orb Acton, Hin-Lap Yip, Hong Ma and Alex K.-Y. Jen

      Article first published online: 31 JAN 2012 | DOI: 10.1002/adma.201290024

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      All-organic photopatterned 4×4 one-diode–one-resistor (1D–1R) cell arrays are presented by Tae-Wook Kim, Alex Jen, and co-workers on page 828. The all-organic type photopatterned 4×4 1D–1R cell array architecture not only improves reading accessibility, but also prevents cross-talk with neighboring cells. Each 1D–1R cell in the array architecture shows excellent switching performance, which suggests that such memory devices can be used for future advanced nonvolatile memory applications.

  9. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Front Cover
    4. Masthead
    5. Contents
    6. Communications
    7. Frontispiece
    8. Communications
    9. Frontispiece
    10. Communications
    1. All-Organic Photopatterned One Diode-One Resistor Cell Array for Advanced Organic Nonvolatile Memory Applications (pages 828–833)

      Tae-Wook Kim, David F. Zeigler, Orb Acton, Hin-Lap Yip, Hong Ma and Alex K.-Y. Jen

      Article first published online: 2 JAN 2012 | DOI: 10.1002/adma.201104266

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      An all organic, photopatterned 4 × 4 one diode-one resistor (1D–1R) cell array consisting of a photopatterned organic schottky diode and organic memory were fabricated and tested. Our results show that the all-organic type photopatterned 4 × 4 1D–1R cell array architecture not only improves reading accessibility, but also prevents cross-talk with neighboring cells. Each 1D–1R cell in the array architecture showed excellent switching performance, which suggests that such memory devices can be used for future advanced nonvolatile memory applications.

    2. Low-Temperature, Solution-Processed and Alkali Metal Doped ZnO for High-Performance Thin-Film Transistors (pages 834–838)

      Si Yun Park, Beom Joon Kim, Kyongjun Kim, Moon Sung Kang, Keon-Hee Lim, Tae Il Lee, Jae M. Myoung, Hong Koo Baik, Jeong Ho Cho and Youn Sang Kim

      Article first published online: 9 JAN 2012 | DOI: 10.1002/adma.201103173

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      Transfer characteristics of ZnO thin-film transistors (TFTs) based on ZnO doped with various alkali metals. A new doping method is demonstrated by employing alkali metals to achieve high-performance and solution-processed ZnO TFTs with a low processing temperature (∼300 °C), which is applicable to flexible plastic substrates.

    3. Anisotropic Charge Transport in Spherulitic Poly(3-hexylthiophene) Films (pages 839–844)

      Edward J. W. Crossland, Kim Tremel, Florian Fischer, Khosrow Rahimi, Günter Reiter, Ullrich Steiner and Sabine Ludwigs

      Article first published online: 3 JAN 2012 | DOI: 10.1002/adma.201104284

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      Macroscopic P3HT spherulitic crystals are grown in 25-nm-thick films via precise control of solvent swelling during polymer crystallization, which allow placement of transistor channels within single oriented crystal domains.Charge-transport anisotropy in the b–c (π-stacking & main chain) plane and the role of order–disorder grain boundaries are reported.

    4. Realization of a High-Performance GaN UV Detector by Nanoplasmonic Enhancement (pages 845–849)

      Dabing Li, Xiaojuan Sun, Hang Song, Zhiming Li, Yiren Chen, Hong Jiang and Guoqing Miao

      Article first published online: 2 JAN 2012 | DOI: 10.1002/adma.201102585

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      Realization of highly responsivity UV detectors is a critical challenge for accelerating the application of UV detectors. Exploiting nanoplasmonic enhancement, Ag nanoparticles have been formed on the GaN surface and the responsivity of the GaN UV detector has been enhanced about 30 times compared with that without Ag nanoparticles.

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